0
$\begingroup$

I’m a (junior) stress engineer and have been tasked with sizing a lug. Various loadcases have been run through FEM and loads have been distributed into the lug bolt for each. In other words, each loadcase has its own set of x, y, and z loads at the bolt.

An initial analysis (spreadsheet) was run, where the lug was sized using the max x, y, and z loads across all loadcases. My understanding is that this is conservative.

Now I’m being asked to take out conservatism by applying case consistent loads. Would I go about that just by doing an analysis for each loadcase with a max value? Am I understanding the meaning of “case consistent”?

As an example:

Loadcase 1 has no maxes, so I don’t even look at it

Loadcase 2 has the max x, so I analyze the lug using all values from this loadcase

Loadcase 3 has no maxes, so I don’t even look at it

Loadcase 4 has the max y, so I analyze the lug using all values from this loadcase

Loadcase 5 has the max z, so I analyze the lug using all values from this loadcase

Sorry for the long post, but any help is appreciated.

$\endgroup$
  • $\begingroup$ Could it mean no cyclic loads? Why not sk the person who gave you the instruction - it came from somewhere. $\endgroup$ – Solar Mike Jul 9 at 7:21
  • $\begingroup$ @SolarMike I’d love to ask the person who gave me these instructions, but unfortunately they’re located out of my country and their email server is down... $\endgroup$ – Hunter Jul 9 at 16:33
  • $\begingroup$ Then apply some commonsense and think about the assumptions you might make. $\endgroup$ – Solar Mike Jul 9 at 16:40
0
$\begingroup$

It quite simply means that when you are doing e.g. a check for the maximum X-force, you should use the Y-force and Z-force (and any bending moments and so on, if applicable) that occurs in the same load combination, and similarly for the other forces.

Note that the procedure you describe, may sometimes be significantly on the unsafe side in with respect to your criteria for disregarding load cases. What if, for example:

  • Load case 1 has 90% X-force and 90% Y-force.

  • Load case 2 has 100% X-force and 10% Y-force.

  • Load case 4 has 10% X-force and 100% Y-force.

In that situation, could case 1 not be more critical than both 2 and 4, even though it has no maximum values?

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.